The production of endothelial cells from pluripotent stem cells such as embryonic stem cells and induced pluripotent stem cells is important because it can be applied to the treatment of ischemic diseases which requires angiogenesis. Endothelial cells are also essential to provide important vascular networks in the field of regenerating tissues such as liver tissues. Although many studies for the induction of differentiation of embryonic stem cells or induced pluripotent stem cells into endothelial cells have been carried out, new cells obtained from these cells are likely to have possibility of cancer induction and to be incapable of differentiation so that a transdifferentiation to endothelial cells by partial reprogramming of mature somatic cells such as fibroblasts can be an alternative [Graf, T. et al., Nature., 2009].
In fact, mouse embryonic fibroblasts have been successfully converted to muscle cells by the MyoD gene and 5-azacytidine [Davis, R. L, et al., Cell, 1987]. Ngn3, Pdx1, and Mafa genes have been introduced into pancreatic exocrine cells, thereby converting into beta cell-like cells that secrete insulin [Zhou, Q., et al., Nature, 2008].
In the case of endothelial cells, Ginsberg et al. firstly introduced ETS transcription factors ETV2, FLI1, and ERG1 into human midgestation c-Kit-linease-committed amniotic cells in 2012 and reported that the induced culture was performed in EGM2 medium in the presence of TGF-beta inhibitor, thereby converting into cells which exhibit the property of endothelial cells (Ginsberg, M., et al., Cell, 2012). These cells were observed to form stable blood vessels in Matrigel plug and regenerated liver tissue. Afterwards, it was reported that only one ETV2 gene could be introduced into human skin fibroblasts and converted into cells showing the characteristics of venous endothelial cells [Morita, R., et al., Proc Natl Acad Sci USA, 2015].
Further, innate immunity was stimulated using a toll-like receptor 3 (TLR3) agonist so that fibroblasts were converted into cells showing the characteristics of endothelial cells [Sayed, N., et al., Circulation, 2015]. Two kinds of genes, Oct4 and Klf4 were introduced to convert into cells expressing endothelial cell characteristics [Li, J., et al., Arterioscler Thromb Vasc Biol, 2013].
In addition, it was tried that Oct4, Sox2, Klf4, and c-Myc which are Yamanaka factors 4 were introduced, but partial reprogramming was performed without induction of iPS production stage, thereby converting into endothelial cells [Margariti, A., et al., Proc Natl Acad Sci 2012]. In the present invention, two genes that are not directly related to cancer induction are selected among the reprogramming factors, and two transcription factors that are expressed at a low level or not expressed in mesenchymal stem cells derived from the umbilical cord are selected among the transcription factors related to vascular development. Thus, a method has been developed to convert adult somatic cells or mesenchymal stem cells (MSCs) which are adult stem cells into endothelial cells by combining these four transcription factors.